A defect-controlled
approach for the nucleation and epitaxial growth
of WSe2 on hBN is demonstrated. The WSe2 domains
exhibit a preferred orientation of over 95%, leading to a reduced
density of inversion domain boundaries (IDBs) upon coalescence. First-principles
calculations and experimental studies as a function of growth conditions
and substrate pretreatment confirm that WSe2 nucleation
density and orientation are controlled by the hBN surface defect density
rather than thermodynamic factors. Detailed transmission electron
microscopy analysis provides support for the role of single-atom vacancies
on the hBN surface that trap W atoms and break surface symmetry leading
to a reduced formation energy for one orientation of WSe2 domains. Through careful control of nucleation and extended lateral
growth time, fully coalesced WSe2 monolayer films on hBN
were achieved. Low-temperature photoluminescence (PL) measurements
and transport measurements of back-gated field-effect transistor devices
fabricated on WSe2/hBN films show improved optical and
electrical properties compared to films grown on sapphire under similar
conditions. Our results reveal an important nucleation mechanism for
the epitaxial growth of van der Waals heterostructures and demonstrate
hBN as a superior substrate for single-crystal transition-metal dichalcogenide
(TMD) films, resulting in a reduced density of IDBs and improved properties.
The results motivate further efforts focused on the development of
single crystal hBN substrates and epilayers for synthesis of wafer-scale
single crystal TMD films.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.